Compound, material for an organic electroluminescent device and application thereof
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Solution Overview
Problem
Current organic electroluminescence materials for capping layers in OLEDs face challenges such as low refractive index, high absorption or extinction coefficient in visible light, poor thermal stability, and incomplete coverage, leading to inefficient light extraction and chromaticity issues, especially for blue light-emitting elements.
Innovation Solution
A compound with a high refractive index and low extinction coefficient in the blue light region, featuring a benzoxazole or benzothiazole-containing group structure, is developed for use as a capping layer material, enhancing light extraction efficiency and external quantum efficiency while minimizing blue light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If materials with high refractive index are used for capping layer, then light extraction efficiency is improved, but absorption in visible light region increases
Solution Approach 1:
The patent changes the chemical composition parameters of the capping layer material by incorporating specific heteroatomic groups (sulfoxide, sulfone, carbonyl) which inherently provide high refractive index. This compositional parameter change allows achieving high refractive index (n>2.1) without the trade-off of increased visible light absorption, as these functional groups contribute to refractive index through their electronic structure rather than through strong visible light chromophores.
Solution Approach 2:
The patent employs composite molecular structures combining electron-transporting moieties with high refractive index functional groups (sulfoxide, sulfone, carbonyl). This composite approach creates materials that simultaneously achieve high refractive index for light extraction enhancement and appropriate optical transparency in the visible region, resolving the contradiction between these two properties.
2Ease of manufacture
If electron-type capping layer material is designed to achieve electron transmission and light extraction, then preparation cost is reduced, but light-emitting efficiency improvement is limited and chromaticity problems remain
Solution Approach 1:
The patent designs capping layer materials that perform multiple functions simultaneously: electron transport (via electron-transporting moieties), light extraction (via high refractive index functional groups), and optical stability (via appropriate HOMO-LUMO gap). This multi-functional design eliminates the need for separate electron transport layers, reducing preparation cost while achieving excellent light-emitting efficiency and chromaticity performance.
Solution Approach 2:
The patent optimizes molecular parameters including HOMO-LUMO energy gap (2.3-3.5 eV) to ensure both electron transport capability and optical transparency. By adjusting these energy parameters through molecular design, the material achieves simultaneous electron transmission and light extraction functions with improved light-emitting efficiency and resolved chromaticity issues.
3Stability of the object's composition
If molecular structure is designed to be large and loose to increase density and achieve high thermal stability, then thermal stability is improved, but molecular gel holes increase during evaporation resulting in incomplete coverage
Solution Approach 1:
The patent introduces localized high refractive index functional groups (sulfoxide, sulfone, carbonyl) within a relatively compact molecular framework. This local quality approach concentrates the thermal stability and refractive index enhancement in specific molecular regions without requiring overall molecular expansion, thereby maintaining good packing density and complete coverage during evaporation while achieving high thermal stability.
4Loss of energy
If capping layer material has high refractive index, then light extraction efficiency is improved, but external quantum efficiency in blue light region is limited due to absorption
Solution Approach 1:
The patent carefully controls the HOMO-LUMO energy gap parameter (2.3-3.5 eV) to ensure the LUMO level is sufficiently deep to prevent absorption of blue light photons (400-450 nm). This energy parameter optimization, combined with high refractive index functional groups, enables simultaneous achievement of high light extraction efficiency and high external quantum efficiency in the blue light region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compound significantly improves light-emitting efficiency and external quantum efficiency, reduces color cast, and provides a longer device lifetime by effectively managing light extraction and chromaticity in organic electroluminescent devices.
Implementation Method 1
the compound has a relatively high refractive index and can effectively improve the external quantum efficiency (EQE) of an organic photoelectric device when used as a material for the capping layer
Implementation Method 2
an optical interference distance is adjusted, the reflection of external light is suppressed, and the extinction caused by the movement of surface plasmon is suppressed
Implementation Method 3
the compound has a relatively small extinction coefficient in the region of blue light (400-450 nm) and hardly absorbs blue light, improving the light-emitting efficiency
Implementation Method 4
organic electroluminescence (such as organic light-emitting diode, OLED) has gained considerable progress
Data Source
AI summary
The present disclosure relates to a compound, a material for an organic electroluminescent device and an application thereof. The compound provided by the present disclosure has a relatively high refractive index and can effectively improve the light extraction efficiency and the external quantum efficiency of an organic electroluminescent device when used in the organic electroluminescent device especially as a material for the capping layer. The compound has a relatively high refractive index in the region of visible light (400-750 nm), which is conducive to improving the light-emitting efficiency. The compound has a relatively large extinction coefficient in the ultraviolet region (less than 400 nm), which is conducive to absorbing harmful light and protecting eyesight and has a relatively small extinction coefficient in the region of blue light (400-450 nm) and hardly absorbs blue light, which is conducive to improve the light-emitting efficiency.